I have a 95 3.0 M3 which starts in the button and runs fine
Then after 5 mins on the drive or 2 mins driving, it drops a cylinder.
But it doesnt just lose 1.
It will go from 6-5-4-5-4-6-3-6-2-1 die.
Its really weird. It first started that it lost 1 cylinder, byt would carry on drivin (badly of course) park it up for a couple of hrs and it would b fine again, for ages.
Gradually it got worse, more cylinders started droppin and it happened sooner and sooner, till now. Its totally undriveable.
Strange thing is sometimes the cylinders pick back up for a short while.
Then leave it over night and it starts fine again.

I have had it on a launch scanner and theres no fault codes stored,
Tried a different ecu off another 95 3.0 m3 thats known to work,
Different coils,
New crank sensor,
New fuel filter,
Different afm
Different tps
Also read live data from sensors when it plays up and all seem ok.
No mayo in oil/water
No lack in performance when it works
No smoke/smells
Not losin oil/water

Engine was rebuilt 10k ago
Everything was perfect before this.

Any1 got any ideas? Ive got a spare car that works i can try parts off.
Any ideas before it goes into a specialists?

Could it be fuel pump related? I would say it was if it only happened under load, but as it happens on the drive at idle it makes me think not. Especially as the cylinders pick back up sometimes.

 

I've had camshaft sensors play about on BM's which cause problems with injector firing if that helps?

 

should see the camshaft sensors fucking up in the live diagnostics tho.

have you changed all the coils? coil failure is common on them

have you done the obvious such as changed the plugs? is the vanos working when it fucks up?

 

if it was a camshaft sensor woudnt the fault be there all the time?
plus as jim says it should show on live data.

yep changed all the coils and it cures the fault for all of 1/2 a road and its back.
plugs are recent and clean and dont show any faults, and again if it was under load and failed it could be plugs, but surely not while just idleing, as its not overfuelling and fouling them like a cossie does.
vanos seems to be working fine.
when it runs ok it has full power, and the vanos is silent.

 

i know this isnt answering the question, but the place i goto is in bexleyheath called Bexley Motor Works and im sure they'd sort out the problem foe you. they're not cheap at 60quid an hour but they always diagnose and fix my problems with no drama. theyve got a very good replucation in the E36 M3 world

 

yea ive heard of em,
i know a couple of people that have been to a place in heathrow, ex bmw with bmw computers.
he charges Ł65 to diagnose the fault then Ł50 an hour to fix it i think.
problem is as the car is undriveable i gotta tow it wherever it goes and neither of them will be a fun place to take it to.
and as i dont know either of them i wanna stay with the car.
so i need to have the time and money to have a day off to go wherever and stay there till its sorted and pay the bill.
lol

but ill happily give it a go at fixin it myself, and having another 1 to try parts from helps

 

do a compression check.